In FIG. 1 a general view of a cellular radio system is depicted with different nodes and interfaces.
In FIG. 1:
A User Equipment (UE) is the mobile terminal by which a subscriber can access services offered by an operator's Core Network (CN).
A cell covers a geographical area. The radio coverage in a cell is provided by a radio base station equipment at a base station site. Each cell is identified by a unique (at least locally unique) identity, which is broadcast in the cell. There may be more than one cell covering the same geographical area.
The BS (Base Station) handles the radio transmission and reception within one or more cells.
The RAN (Radio Access Network) is the part of the network that is responsible for the radio transmission and control of the radio connection.
The RNS (Radio Network Subsystem) controls a number of Base Stations in the radio access network.
The RNC (Radio Network Controller) controls radio resources and radio connectivity within a set of cells.
A Radio Link is a representation of the communication between a UE and one cell in the Radio Access Network.
Iub/Iur interfaces: Interfaces connecting the different nodes in the RAN. User data is transported on so-called transport bearers on these interfaces. Dependent on the transport network used, these transport bearers are for example mapped to ATM Adaption Layer 2 (AAL2) connections (in case of an Asynchronous Transfer Mode (ATM) based transport network) or User Datagram protocol (UDP) connections (in case of an Internet Protocol (IP) based transport network).
Furthermore, each node in the radio access network is connected to an operation and maintenance system, typically one or several domain manager (DM) nodes. The DM maintains software upgrades of the nodes, configuration management, and fault and performance monitoring.
In order to align the network operation over several domain managers, possibly from different vendors, there is typically a network management system (NMS) mastering the domain manager operation.
Uplink Radio Resource Management (RRM) In the Third Generation Partnership Project (3GPP) release 99, the RNC controls resources and user mobility. Resource control in this framework includes admission control, congestion control, channel switching, which typically includes changing the data rate of a connection. Furthermore, a dedicated connection is carried over a dedicated channel DCH, which is implemented as a DPCCH (Dedicated Physical Control Channel) and a DPDCH (Dedicated Physical Data Channel).
In the evolved third generation (3G) standards, the trend is to decentralize decision making, and in particular the control over the short term data rate of the user connection. The uplink data is then allocated to Evolved DCH (E-DCH), which is implemented as a DPCCH, which is continuous, and an evolved DPCCH (E-DPCCH) for data control and evolved DPDCH (E-DPDCH) for data, and the two latter are only transmitted when there is uplink data to send. Hence the radio base station Node B uplink scheduler determines which transport formats each user equipment can use over E-DPDCH. The RNC is however still responsible for admission control.
A UE in idle state monitors the system information of a base station within range to inform itself about candidate base stations in the service area etc. When a UE needs access to services, it sends a request over a random access channel (RACH) to an RNC via a suitable base station, typically the one with the most favorable radio conditions. Since the uplink propagation is only approximately known, the UE gradually increases the transmission power until either the message has been acknowledged, or the maximum number of attempts has been reached, see Radio Resource Control, 3GPP TS 25.331. After admission control, the RNC initiates a connection via a base station if there are available resources. Uplink coverage is thus a necessity in order to successfully complete random access.
In the uplink for a Wideband Code Division Multiple Access (WCDMA) system, there is a trade-off between coverage and enabled peak rates. This is even more emphasized with enhanced uplink, which supports higher bit rates than traditional dedicated channels. The uplink resources are limited by the rise over thermal (RoT) that the cell can tolerate, where the RoT is defined as the total received power divided by the thermal noise power. A limited RoT is either motivated by coverage requirements or power control stability requirements. When only one user is connected in the cell, both power control stability and coverage are minor issues, since the uplink interference is likely to be dominated by the power generated by this user. In such a case it is tempting to allow a high RoT in order to allow a high signal to interference ratio Ec/Io, which enables the use of high uplink bit rates. Conversely, in order to use the high uplink bit rates, the user connections have to provide high Ec/Io, which implies high RoT.
Denote the UE power level in linear scale by p, the maximum power level by pmax, the power gain between the UE and base station by g, the total received power at the base station by I, the thermal noise by N, the signal to interference and noise ratio (SINR) by γ, the required signal to interference and noise ratio by γrec, the non-orthogonal fraction of the interference power contribution by the UE (i.e. the interference contribution fraction that the receiver is sensitive to, or unable to suppress by its receiver means) by α,
Then some expressions relevant for the UTRAN uplink situation includes                Rise over Thermal:        
  RoT  =      I    N                  UE Signal to Interference plus Noise Ratio (SINR):        
  γ  =                    E        c                    I        o              =                  pg                  I          -                                    (                              1                -                α                            )                        ⁢            pg                              ≥              γ        rec                            Corresponding UE power:        
  p  =                    I        g            ⁢              γ                  1          +                                    (                              1                -                α                            )                        ⁢            γ                                =          N      ⁢              RoT        g            ⁢              γ                  1          +                                    (                              1                -                α                            )                        ⁢            γ                                              Required UE power to meet service requirements:        
            p      max        ≥    p    =      N    ⁢          RoT      g        ⁢                  γ        rec                    1        +                              (                          1              -              α                        )                    ⁢                      γ            rec                              
This means that if the RoT operation point is too high, some UEs will be unable to meet the quality requirements in terms of γrec due to insufficient power.
Today, the RoT limitation is typically set to a system-wide value corresponding to an expected worst power gain g in a cell, and a supported quality level γrec. Potentially, some cells with worse power gains than expected will therefore correspond to insufficient service coverage. Moreover, some other cells with better worse power gains than expected operate at a lower RoT than needed, which gives under-utilization of the radio resources since UEs could send with higher power, resulting in higher Ec/Io, and consequently higher bit rates.
Hence there exist a need for new methods and devices providing improved performance in cellular radio systems.